North Korea's state media refrained from using a derogative term in referring to US President Donald Trump, apparently toning down its rhetoric against him ahead of a historic bilateral summit.

Last year, Trump and North Korean leader Kim Jong-un exchanged threats and insults against each other. Trump belittled Kim as "Little Rocket Man," while the North called Trump the "mentally deranged US dotard."

In an article on Washington's move to slap tariffs on imported steel and aluminum, the Rodong Sinmun, the official newspaper of the ruling Workers' Party of Korea, referred to Trump simply as the US leader.

US President Donald Trump (L) and North Korean leader Kim Jong-un (Yonhap)

"Recently, the US leader issued an executive order to impose a 25 percent tariff on imported steel and 10 percent on aluminum," the newspaper said. "If this is carried out, Western countries trading with the US and many steelmakers and aluminum producers will suffer significant damage."

Trump has agreed to an invitation by Kim to meet after a year of heightened tensions over North Korea's nuclear and ballistic missile tests. The summit, which Trump said would take place by May, would be the first between a sitting US president and a North Korean leader.

North Korea's state media has kept mum toward Kim's planned summit with Trump, and a separate meeting between Kim and South Korean President Moon Jae-in slated for late April.

Seoul's unification ministry said Monday that Pyongyang appears to be cautious about its stance toward the meetings and needs more time.(Yonhap)